Research Product

This paper discusses the potential effects of drilling fluids on semi-enclosed bodies of water such as estuaries. Fluids used in the extraction of oil and gas in off-shore and coastal waters are composed chiefly of a mixture of barite, water and chemical additives and are pumped into the well through drill pipe and drill bit. Such fluids serve a number of purposes including cooling the rotary drill bit, lubricating the drill strings and forming a plaster on the sides of the drill hole. Drilling fluids can be discharged directly into receiving waters or they can be removed from the drill site and disposed at sea or terrestrial sites. Drilling fluids have been discharged into outer continental shelf waters for many years but there is some concern of potential ecological impact when drilling fluids are discharged near coral reefs or in bays and estuaries. The concern is based on potential adverse effects of the fluids to corals, shellfish, fish, grass beds and general productivity. Potential effects can be evaluated through a hazard assessment process that involves effects and exposure measurements. A suggested hazard assessment involving the Adaptive Environmental Assessment Approach (AEA) is presented. The components of the AEA approach are described and evaluated. In developing the hazard assessment, a review is made of existing effects data. A presentation is made of issues of concern such as resuspension of drilling fluids in shallow, wind driven estuaries, restriction of light penetration to primary producers by suspended sediments, changes in benthic communities and their substrates, and direct toxicity of the fluids to organisms.